We present the use of a liquid crystal spatial light modulator to correct for the refractive-index mismatch induced spherical aberration in a high refractive-index lithium niobate crystal when a low repetition rate amplified laser is used for the direct fabrication of three-dimensional micro-structures. By correcting the aberration based on experimentally determined values, we show that the size of written structures decreases dramatically, which allows the fabrication of high quality micro-structures such as three-dimensional photonic crystals. We demonstrate that, through the use of adaptive optics, the fabrication depth and the stopgap strength in the corresponding photonic crystals are increased by a factor of two to three.

The authors acknowledge support from the Australian Research Council (ARC) Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), Innsbruck Medical University, EPSRC (EP/E055818/1) and the Leverhulme Trust.